Refractory and method of making the same



April 20, 1948.

c. G. SILVER-BERG REFRACTORY um usraon OF mxms was sum Filed Jan. 16, 1945 IN VENT OH CHBL G vS/L. VERSE? 6 BY v ATTORNE Y f Patented Apr. 20, 1948 I 2,440,187 REFRACTORY AND METHOD or MAKING THE SAME Cari G. Silver-berg,

American Optical Mass., a voluntary ass 13 Claims.

This invention relates to refractory devices and has particular reference to novel means and methods of making the same.

One of the principal objects of the invention is to provide a refractory device for supporting an article to be heated whereby the said device inherently possesses characteristics which will obviate any tendency for the article'being heated to adhere to the refractory device during said heating operation and has particular reference to novel means and methods of making the same.

Another object is to provide refractory devices of the above character which are particularly adapatable for use in supporting a glass article during heating whereby the resultant article will more accurately respond to the heat treatment and will be of more uniform shape resulting from said heat treatment.

Another object is to provide refractory devices of the above character which may be more accurately controlled as to surface shape whereby a glass blank supported by said article and subjected to heat treatment with a view to dropping said blank to the surface shape of said device may be more efficiently and uniformly formed with less tendency of the glass material of said blank adhering with the refractory device during said heat treatment.

Another object-is to more uniformly control the distribution of heat during .the heating operation.

Another object is to provide refractory devices of the above character inherently possessing means for more positively controlling the distribution of heat during the use of the device and which will enable the heating operations to be performed with a requirement of a minimum of time as compared with prior art methods.

Another object is to provide refractory devices of the above character enabling the heating operations to be performed in a minimum of time and with less tendency of breakage of the article or the block during said heating operation.

Another object is to provide novel means'and methods of forming refractories of the above character whereby the supporting surface shape of the refractory may be more positively and accurately controlled.

Another object is to provide refractory devices of the above character whereby the supporting 'surface shape may be altered after themain refractory device has been fabricated.

Brookfleld, Mesa, assignor to Company, Southbridge, ociation of Massachusetts Application January 16, 1943, Serial No. 472,604

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings and it will be apparent that many changes ma be made in the details of construction, arrangement of parts and steps of the methods shown and described without departing from the spirit of the invention as expressed in the accompanying claims. I, therefore, do not wish to be limited to the exact details of construction, arrangement of parts and methods shown and forms only have been given by way of illustrae tion.

Referring to the drawings:

Fig. 1 is a sectional view through a mold block illustrating one step in the process of manufacture;

Fig. 2 is a view generally similar to Fig. 1 illustrating a further step in the process of manufaeture; I

Fig. 3 is "a longitudinal sectional view of a modified form of molding device;

Fig. 4 is asectional view taken as on line 4-4 of Fig 3 and looking in the direction indicated by the arrows;

Fig. 5 is a sectional view generally similar to Figs. 1 and 2 with a further modification of the invention; and

Fig. 6 is a diagrammatic illustration of a refractory block in use in supporting an article to be dropped in the furnace.

scribed of silicon carbide which, at low heating temperatures, produces fairly satisfactory results but in many instances, particularly when joining two or more pieces of glass together by fusion and at the temperature required for said fusion, difficulty Was encountered in having the glass engaging the refractory adhering to the surface of the refractory. In order to overcome or reduce the above difficulty, it has been necessary in most instances in the past to treat the surface of the refractory, as by dusting with clay or graphite. This requirement rendered such prior art refractories impractical for use in dropping glass blanks or articles to controlled surface curvatures as, in most instances, the particles of the dusting material present on the supporting surface of the refractory caused surface distortions in the dropped article. This also introduced difficulty in fusion as one of the essentials to successful fusing is that the atmosphere be as free from dust particles as possible during the assembling of theparts to be fused and during the actual fusing operation. It is quite apparent, when such dusting of the supporting surface is required, that described as the preferred tion. As a further the particles of the dusting material might be deposited on the surfaces of the glasses to be fused with the danger of ruining the fusing operation.

The above difficulties have been definitely overcome by the present invention in that the refractory devices embodying the invention do not require dusting as they inherently possess characteristics which will permit the use of high temperatures with no danger of adhesion of the surface of the glass article in engagement with the refractory device.

Another advantage of the present invention is that the distribution of the heat may be controlled during the heating operation.

A still further advantage is that the surface shapes of the dropped or heated articles may be more positively controlled during said heating so that the resultant surface of the article will be more optically accurate than has hitherto been possible to obtain.

Another advantage is that the initial fabrication of the refractory may be more efficiently performed.

Referring to the drawings wherein like characters of reference designate like parts throughout the several views, the major ingredient used in forming the refractory is kyanite. This ingredient has initially dry characteristics but by proper milling and reducing of said ingredient to fine powdered form and by the addition of a small amount of water, it is possible to shape the material to the shapes desired. It has, however, been found that the addition of plastic clay of any of the various refractory ball clays which will not introduce vitrification may be added as a binder to greatly facilitate the fabrication of the refractory. It is to be understood that any mention of ball clay hereinafter refers to a refractory clay having plastic characteristics.

The addition of sodium silicate to the above ingredients introduces greater ease of fabricaaid, sodium carbonate may be added. Sodium silicate and sodium carbonate are added mainly to introduce greater dispersive characteristics and to facilitate ease in handling the resultant compound.

To further stabilize the compound a small amount of triethanolamine may be added. This,

. of course, depends upon the method of fabrication of the article and will provide additional dispersive characteristics. To reduce the compound to a more fluid state water may be added The amount of water to be used will be determined by the method of fabrication employed.

One of the preferred compositions is as follows:

Approximate Grams Parts by Weight Kyanite 3, 200 8, 000 Ball lay 800 2, 000 Sodium Carbonate. 4 10 Sodium Silicate- 8 20 'lrlethanolamine 2 Water 1, 000 2. 500

Kyanite has a tendency to expand on heating while ball clay has a tendency to shrink so that by controlling the proportions of each according to their tendencies to shrink or expand one can be made to overcome the other so that a more definite size control can be maintained.

The amount of sodium silicate and sodium carbonate must be maintained at a minimum to prevent fluxing and possible adhesive characteristics in the resultant refractory. The amount of said materials used therefore is only that which is sufficient to bring about the desirable working characteristics and said characteristics can be accomplished without the introduction of any adhesive characteristics. Although sodium silicate, sodium carbonate and triethanolamine have been set forth above as good dispersing agents, it is to be understood that any one or all of said materials may be replaced by one or more of the following ingredients:

Morpholine, lignin, Tannic acid or any or agents.

With proper temperature and time controls, a refractory formed of the above materials or compositions will produce very satisfactory results with no danger of adhesion of glass or material of the article being dropped with the refractory during the heating operation.

It has been found, however, that much more satisfactory results can be obtained b the addition of chrome oxide, rouge, manganese dioxide or other known ceramic colorants which do not produce vitrification to any one of the refractory compositions set forth above. The preferred ingredient. however, is chrome oxide which, in a preferred composition, comprises 0 to 25% replacing kyanite in the body, that is, when chrome oxide or one of the other colorants set forth above are used, the kyanite is reduced correspondingly. The purpose of adding the above colorants to the refractory composition is to more uniformly control the distribution of heat throughout the article being supported and also throughout the refractory itself. The above colorants are infrared absorbing materials which during the heating of the article being supported tends to absorb the heat. This absorption of the radiant heat provides a more uniform heating of the refractory.

It is to be noted that green chrome oxide is set forth above as the preferred infra-red absorbing sodium gallate, etc. other known dispersive agent ingredient. It is to be understood, however, that rouge or manganese dioxide may be used. It has been found that when rouge or manganese dioxide is used the initial refractory produces very satisfactory results but upon repetitive use the said refractories tend to lose their efiiciency as to infra-red absorption. In instances, however, when the said refractories are not required for repetitive use such infra-red absorbing ingredients are practical for use but in instances when the refractories are for repetitive use green chrome oxide produces much more satisfactory results.

In addition to introducing the desired infrared absorbing characteristics, such ingredients introduce a greater resistance to adhesion in the resultant device. This is particularly true of green chrome oxide.

One of the preferred methods of forming the composition is as follows:

A. First dissolve one or more of the dispersin agents set forth above in the required amount of water.

' added to the batch or mix.

about mixingas' without forming large lumps. The resultant mixture will be fairly smooth.

E. To the above, although not absolutelyessential, a small amount of triethanolamine is The mixture resultingfrom the combining of the above ingredients is then preferablymilled in a suitable ball mill or the like for a period of 70 to 80 hours. The mixture is then ready for use. r I

The preferred composition is substantially as follows: A

If the said mixture is to be kept for some time prior to its being used a small amount of formaldehyde solution is added, either before or after the milling, as a preservative. Approximately 1 cc. of 40% formaldehyde solution. a ded to t preferred batch set forth above has been found to produce desirable results. It is to be understood that the said mixture is preferably placed "in a closed container to prevent evaporation and loss of moisture.

In Fig, 1 there is illustrated a mold member 6 suitable for use with a fluid mixture such as set forth above. This mold member is preferably a formed of plaster of Paris or other suitable porous material and is provided with a recess 1 having its internal walls and bottom 8 formed substantially to the shape desiredof the resultant refractory.

A suitable amount of fluid composition 9 is poured into the recess and due to the porosity of the plaster of Paris or other similar material from which the mold i is formed a certain amount of the water is absorbed by the said porous material, particularly, throughout the surfaces which are in contiguous relation with the fluid composition 9.- This action causes a superficial hardening of the composition throughout said surfaces tending to build up to a considerable thickness when allowed to set for a relatively short period of time. It has been found that if the mold is relatively dry and porous that within a period of minutes a wallth'ickness suitable for small articles will be built up. The fluid which has not reached a solid state is then poured from within the built-up wall of the composition leaving a central cavity ID, as shown in Fig. 2. The material which has been removed from the cavity may be used for other reg ams..- 2400 The above is a very simple form of mold and is used in instances when only one shape of surface is desired.

In instances when the opposed sides of the supporting block are to be shaped to a given shape a mold similar to that shown in Figs. 3 and 4 may be used, this mold comprising a plurality of spaced blocks H held in spaced relation with each other by a band of metal or other suitable material I: which is inserted within a suitable retaining block ii. The band I2 is provided with spaced deflected lip portions it which provide means for gaining access to the interior of the moldbetween the blocks Ii. The blocks ii may be formed of plaster of Paris or other porous materials such as set forth above. The

' blocks H are placed in spaced relation with each other by the amount required of the resultant thickness of the refractories and by providing a plurality of spaced blocks several refractories v may be formed in a single casting operation. The

fluid composition is poured inwardly of the mouth v formed by the spaced lips it between the blocks Kyanite Ball clay "do..-" 800 Chrome oxide (green) do 800 Sodium carbonate do 4 Sodium silicate do.. 8 Triethanolamine c c 2 Water grams 100.0

II. The composition is allowed to remain in the mold until it has reached a desirable hardened statewhereby the contiguous surfaces of the blocks and the composition are separated through the contraction of the composition. The blocks together with the molded refractories are then slid outwardly of the retaining block I3. The band I4 is then removed whereby the several blocks and resulting refractories may be separated. After each casting operation the blocks II have to be dried out so as to have the proper porosity.

In Fig. 5 there is diagrammatically illustrated another method of forming the refractories. In

this view, there is illustrated a die member ii in which the composition iii to be molded is placed and a suitable plunger I1 is provided for compressing the materialinwardly of the cavity of the die. In this instance, the composition does not have the fluidity of the above mentioned composition. Less water. is used and the composition is in the form of a distortable mass [6. The amount of the composition It is controlled according to the resultant size of the refractory desired. It is to be understood that the die I5 is provided with an inner surface It which is substantially the shape desired of the supporting surface of the refractory. Upon removal of the cause the disintegration of the refractories fractories. If desired, however, the entire deposit i 1 will takeplace throughout all of the contiguous surfaces.

through the formation of steam during said drying andcare must also be taken that the drying takes place substantially uniformly throughout the refractories. The dried'refractory blocks, if placed in water, will have a, tendency to disintegrate and, therefore, must be fired at a higher temperature. This firing is accomplished by increasing the temperature of the heat in the furnacesin which the drying operation has been performed or by placing the said dried refractories in another furnace or suitable heating de- From room temperature to 400 F. by raising the temperature at 100 F. per hour 200 F. per hour to 800 F. 400 F. per hour to 2200 F.

The furnace is held at 2200 F. for approximately five hours. If smaller furnace is used temperature rates would be increased and time decreased, if larger articles are made the temperature changes must be very much slower and time intervals lengthened.

From the above, it will be seen that the temperatures are increased gradually until the desired maximum temperature is obtained. This firing is for the purpose of bringing about a positive bond between the particles of the composition tending to produce a refractory having the desired supporting characteristics.

Although the temperature schedule set forth above gives the 2200 F. temperature as the high limit it is to be understood that higher or lower temperatures may be used for the final tempera- "ture. The upper temperature limit, however,

must be such as to avoid vitrification or the formation of any glassy phase in the refractory. The firing temperature, however, which will produce vitrification is much above that required in the subsequent heating of articles which are to be supported and dropped through the action of heat so that there will be no inherent danger of vitrifi cation taking place during the actual use; of the refractory. Firing at relatively low temperatures, say below 1800 F.,'causes the resultant refractory to be relatively soft and less resistant to wear and breakage. Above 1800 F. and at approximately 2200 F. the refractory is much shown a refractory block 2| formed by any of the methods set forth above. This refractory block has a supporting surface 22 thereon formed either during the fabrication of the block or by subsequent shaping. On the supporting surface 22 there is'shown an article 23 to be dropped by heating. The article 23 may be a glass blank which is to be heated to a temperature sufficient to caluse the material of said blank to drop through gravital action and conform to the surface shape of the supporting surface 22. It is to be understood that instead of using the refractory 2| for the purpose of dropping a blank, such as set forth above, the said refractories may be used for several other operations, for example,

for supporting a major blank during the fusion of a minor blank thereto as is common practice in the forming of bifocal or multifocal ophthalmic lenses. The refractory block is of such a nature more resistant to wear and to breakage and yet v is of such a nature that the supporting surface may be readily shaped by grinding or other suitable means. When the firing temperature is increased considerably above 2200 F. there is not only a danger of vitrification of the composition but there is a danger of deformation during firing and the introduction of extreme brittleness and difliculty in shaping. However, for certain purposes we have found that temperatures above 2200 F. may be desirable, especially when increased hardness is desired. One particularly desirable temperature is 2250 F.

The composition set forth above is of such a nature that even after firing the supporting surface or surfaces of the refractory may be built-up through the use of an additional amount of, unfired composition. This is particularly important when portions of the supporting surface are required to be altered to obtain more accurate shaping. This is accomplished by first saturating the refractory block with water or more particularly the surface thereof which is to be builtup. A given amount of unfired composition is then placed on the supporting surface in the vicinity which is to be built-up. The said builtup portion is then shaped to the-resultant shape desired and the block is then initially dried and subsequently fired in the above manner. If there is to be an appreciable amount of building up this may be accomplished through successive stages in the above manner. This is found particularly useful when the refractory'has been accidentally scratched or otherwise injured.

In Fig. 6 there is diagrammatically illustrated that the surface of the article engaging the supporting surface of the refractory 22 will have no tendency to adhere to said supporting surface and does not require the use of additional materials as a preventative for said adherence.

Another very desirable characteristic of the present invention is that the refractories do not become altered or distorted as to shape through continued use.

Although kyanite is set forth as the preferred major constituent it is to be understood that andalusite or sillimanite may be substituted for such kyanite or mixtures of andalusite, kyanite,

and. sillimanite may be used. Clays or other ingredients having an alumina content approach-- ing kyanite may also be used. Care should be taken, however, that the temperatures used in I firing and that the temperatures at which the said resultant refractories are to be used are below that which would cause vitrification.

In instances where high alumina content ingredients are used, such as high alumina clays it might be necessary to subject the said ingredient to an initial firing or dehydration process. This, however, is'not essentialwith the kyanite, andalusite and sillimanite materials as these materials are inherently anhydrous.

-Kyanite, andalusite and sillimanite have characteristics which are such that no vitrification.

takes place within the range of temperatures to which they are to be used in the present instance as the articles which are to be heat treated are in most instances glass articles.

The above mentioned ingredients, kyanite, an-

dalusite, and sillimanite are aluminum silicates which inherently contain no water of crystallization and are given herein as examples of ingredients which are suitable for forming refractories 0f the character described. They are all anhydrous aluminium silicate minerals having an alumina silica ratio of approximately 1 to 1, that is, 1 A: and 1 S102.

From the foregoing description it willbe seen that simple. efficient and economical means and methods have been provided for accomplishing all of the objects and advantages of the invention.

Having described my invention, I claim:

1. The method of forming a refractory suitable for heat dropping glass articles comprising forming a mixture of an ingredient having a high aluminous silicate content in substantially anhydrous state, ball clay, an infra-red absorbing ingredient and water with the ingredient of high aluminous silicate content beingv in excess of the ball clay and the infra-red absorbing ingredient being controlled according to the infral I I 9 red absorbing characteristics desired shaping said composition to produce a refractory having a supporting surface of substantially the shape desired to be formed on the glassearticle, subiecting said shaped refractory to heat of-arela tively low temperature to. remove the waterand subsequently subjecting said refractory to heat of a relatively high temperature with the maximum temperature being substantially above the temperature at which the glass articles will initially soften and controlled to introduce the proper binding action of the ingredients of the composition with no vitrification and so that a non-vitrifled body substantially non-adhesive to glass in the presence of heat sufficient to soften the glass remains.

2. The method of forming a refractory suit-- able for heat d ropping glass articles comprising forming a mixture of an ingredient having, a high aluminous silicate content in substantially anhydrous state, ball clay, green chrome oxide and water with the ingredient of high aluminous silicate content being in excess of the ball clay and the green chromic oxide being of an amount to introduce the infra-red absorbing characteristics desired, shaping said composition to produce a refractory having a supporting surface of substantially the shape desired to be formed on the glass article, subjecting said shaped refractory to heat of a relatively low temperature to remove the water and subseuuently subjecting said refractory to heat of a relatively high temperaturebeing substantially above the temperature at which the glass softens and with the, maximum temperature controlled to introduce the proper binding action of the ingredients of tion and so that a non-vitrified body substantially non-adhesive to glass in the presence of heat sufiicient to soften the glass-remains.

3. A refractory having a surface of controlled shape for supporting a glass article to be dropped thereon under the action of heat that is substantially non-adhesive to said article in the presence ofheat of an amount sufficient to soften the article, said refractory comprising a nonvitrifled body consisting of a mixture of kyanite and ball clay with said kyanite being in excess of said ball taining a dispersing agent and an ingredient having infra-red absorbing characteristics, the ingredients of said mixture being heat joined with each other at a temperature above the softening point of the article to be softened but below the point of vitrification of said mixture.

4. A refractory suitable glass articles comprising a non-vitrified body substantially non-adhesive to said article in the presence of heat of an amount sufficient to soften said article, said body being formed hollow and with a. top portion of substantially uniform thickness having a supporting surface of a shape controlled to impart the shape desired to a surface portion of said article, said body consisting of kyanite, ball clay and green chrome oxide as an added infra-red absorbing ingredient with the kyanite being in excess of said ball clay and green chrome oxide and with the amount of said green chrome oxide being controlled according to the infra-red absorbing characteristics detired.

5. A refractory for use in supporting glass at softening temperatures and non-adhesive to said clay and with the said mixture conglass at said temperatures, comprising essentially a highly refractory aluminous silicate mathe composition with no vitrificafor use in droppin 1 ""7 JTIT terial-coiniii'fiemgreen chrome oxide of an amount suiilcientrto produce. long wave infrared absorption and containing suitable nonvitrifying bonding material with said ingredients being bonded with each other at a temperature substantially above the temperature at which the g --tobeesupported will soften but substantially below the temperature at which any fusion or vitrification of the ingredients takes place.

6. A refractory for use inheat dropping glass articles that is non-adhesive to the articles in the presence of. heat suflicient to soften 'the articles, said refractory comprising a plurality of heat joined ingredients including as a major ingredient a high alumina mineral. ball clay as a binder of an amount which, with the temperature required to produce said heat joining, willvitrification, a dispersing agent and a colorant of an amount for introducing desired infra-red absorbing characteristics, the heat joining temperature being substantially above the tempera- "ture required for said heat dropping of said glassarticles but being below the temperature at which fusion or vitrification of the ingredients takes place.

- 7. A refractory for use in heat dropping glass articles that is non-adhesive to the glass at the softeningtemperature thereof consisting essentially of a highly refractory aluminous silicate mineral combined with green chrome oxide upwardly to approximately 25% depending upon the infra-red absorbing characteristics desired, said ingredients being heat joined with each other at a temperature such that no vitrification takes placejbut substantially above the temperature at which the articles with which the refractory is to be used softens.

8. A refractory suitable for use in heat dropping a glass article that is substantially nonadhesive to the glass in the presence of heat suflicient to soften the glass, said refractory comprising a body portion essentially of kyanite in combination with ball clay of from 0 to 35% of the total composition and green chrome oxide of an amount upwardly to approximately 25% upon the infra-red absorbing characof sodium silicate, sodium carbonate and the temperature of heating being so controlled as to L that the resultant refrac- .avoid fluxing and so tory is free from a classy phase and possesses non-adhesive characteristics as to the glass article being dropped in the range of temperatures at which the glass softens 'sufliciently to drop.

' 9. The method of forming a refractory suitable for heat dropping glass articles comprising forming a mixture of kyanite, ball clay, green chrome oxide and water with the green chrome oxide being controlled according to the infrared absorbing characteristics desired, shaping the composition to the shape'of the refractory desired, subjecting said refractory to heat of a relatively low temperature to remove the water and subsequently subjecting the said refractory to heat of a temperature substantially above the temperature at which the glass articles soften and controlled so as to introduce aproper binding of the ingredients with no vitrification.-

10. A refractory suitable for use in heat drop-.

ping glass articles comprising a body portion embodying 11. A refractory for use in heat dropping glass blanks that will be substantially non-adherent to the glass of the blanks in the presence of heat sufficient to soften said glass comprising a body portion embodying substantially:

Per cent by weight 60 Kyanite Ball clay 20. Green chrome oxide 20 12; A refractory for use in heat dropping glass blanks that will be substantially non-adherent to the glass of the blanks in-the presence of heat suflicient to soften said glass comprising a body portion embodying substantially:

, Per cent by weight A highly refractory aluminous material 60 Ball clay 20 Green chrome oxide 20 13. A refractory foruse in heat dropping glass articles that is substantially non-adhesive to the articles in the presence of heat sufficient to soften the articles, said refractory comprising a plurality of heat joined ingredients including as a major ingredient a high alumina mineral, ball clay as a binder-of an amount which, with the temperature required to produce said heat joining, will introduce a greater ease of fabrication with no vitrification, and a colorant of an amount for introducing desired infra red absorbing characteristics; the heat joining tempera.-

ture being substantially above the temperature required for said heat dropping of said glass articles but being below the temperature at which vitrification of the ingredients takes place.

CARL G. SILVERBERG REFERENCES CITED The following references are of record in the file of this patent:

STATES PATENTS Number Name Date 94,726 Eaton Sept. 14, 1869 15 637,635 Mersch Nov. 21, 1899 700,673 Buchner May 20, 1902 1,081,536 Jeppson Dec. 16, 1913 1,292,953 Jeppson et al. Jan. 28, 1919 1,631,695 Riddle June 7, 1927 1,682,675 Horsfleld Aug. 28, 1928 1,712,005 Lambie et al. May 7, 1929 1,716,395 Trostel June 11, 1929 1,760,360 Hood May 27, 1930 1,769,297 Lambie et al. July 1, 1930 1,812,376 Ross et al. June 30, 1931 1,856,613 Ackermann May 3, 1932,

1,897,183 White Feb. 14, 1933 1,909,785 McDougal May 16, 1933 1,942,879 Riddle Jan. 9, 1934 2,079,715 Pole May 11, 1937 2,159,349 Bennett May 23, 1939 2,160,873 Kerla June 6, 1939 2,207,558 Singer July 9, 1940 2,270,607 Ryschkewitsch Jan. 20, 1942 2,272,039 Morgan Feb. 3, 1942 2,308,473 V Wadman et a1. Jan. 12, 1943 2,331,232 Ross Oct. 5, 1943 1 FOREIGN PATENTS 0 Number Country Date 676,595 Germany 1989 

